The present invention generally relates to fastening systems and more particularly pertains to a self-piercing, threaded fastener, joint and machine.
It has recently become known to employ hydraulic and electric motor actuated machines to insert self-piercing rivets into sheet metal panels. For example, an electric motor-based device is disclosed in U.S. Pat. No. 6,276,050 entitled “Riveting System and Process for Forming a Riveted Joint,” which issued to Mauer et al. on Aug. 21, 2001; this patent is incorporated by reference herein.
A conventional clinch nut has also been employed for use with a single thickness, sheet metal, automotive panel. A slug is pierced from the panel by the nut and a ram of a setting machine thereafter removes the slug. Thus, an unobstructed hole is present from one side of the panel to the other through the nut. This is disadvantageous in that dirt, vehicle exhaust and other debris can move from one side of the panel to the other through the hole. Another conventional system provides a clinch stud used with a pre-drilled hole in a single sheet metal panel. A pneumatic setting machine is employed for both the traditional clinch nut and clinch stud systems. This has considerably different controllability and operational characteristics than an electric motor actuator. Furthermore, other traditional clinch nuts and clinch studs employ a pre-pierced panel opening, prior to insertion of the nut or stud, which adds an expensive extra manufacturing step and complexity to the setting tool, as well as adds undesirable additional tolerance variations which may lead to the creation of vehicle noise and vibration at the joint.